That's cool. And not a huge surprise. Hitec and FMA RXs use the same crystal (according to the FMA tech I talked to), and I interchange them all the time. (I fly combat competitions, so I change channels a fair bit). Other guys I know have interchanged Futaba and Hitec, though I haven't done so myself. So it appears likely that there is a "standard part" crystal being used by many RX designers.

Btw, this would only apply to duel conversion RXs. A single conversion RX (such as a GWS micro RX (I have one of those in a park flyer) would use a different crystal for sure. Also, JR brand gear seems to use a different crystal, and their receivers are apparently not duel conversion the typical sense, they use a different technique apparently.